Sidney Love Harte

"The dart worked."

-Her shooting Sidney in the neck.

She is an old teacher and she is now a survivor in the apocalypse. She does tests on people during the apacolypse.

Season 4
She is a 28 year old woman who used to teach. She finds out Klaire is immune to zombie bites and assumes they should disect her. She tries to rob the twins and take their bag of weapons and then gets shot at and runs away.

Backstory
In her Centric Episode it is revealed she used to be Jake and Marley's teacher.